Thank you, the link worked 
Ah, good to know it works now
Problem resolved, but now I want to learn about this system restore
Firstly, how can you define any set up to be 'working', etc
What exactly are these set ups
Would system restore have installed that program?
If it is a last resort, why were people recommending I do it =/ what do you do before then
Only the user can really define if a computer is working or not - if something's not working how it usually does, e.g. in your case the scroll on the trackpad stopped working.
How your computer is 'set up' is basically the combination of the computer's settings, all the installed drivers, software etc. The way I described it is a bit ambigous lol, but I don't know how else to put it, sorry.
System Restore is a
bit (emphasise a bit) like wiping the slate clean and starting over.
An exaggerated analogy is formatting your computer if you have a problem. You would try fix the problem first rather than just formatting straight away. This is why it's a last resort - you don't really want to alter your computer too much unless you really have to.